A valve drive of this type is previously known from DE 199 56 584 A1; in said document, it is what is known as a desmodromic valve system having a lifting disk valve which is actively loaded with a stroke by a tappet of an actuator, not only in the opening direction but also in the closing direction. The valve closing force of the lifting disk valve, which valve closing force is active with respect to the valve seat, is generated by a spring means; although the spring force of said spring means is substantially independent of the stroke profile of the lifting disk valve, said spring means is clamped in between the tappet of the actuator and the lifting disk valve and as a consequence moves in its entirety completely with the lifting disk valve. This is true to the same extent of the valve drive which is proposed in U.S. Pat. No. 1,232,352.
In the case of the spring means being coupled to the lifting disk valve in this way, the spring means represents, however, in both cases an additional mass, which is moved completely with the lifting disk valve and conflicts with the general aim in the design of valve drives, namely to minimize their drive and contact forces with a high ability to withstand high rotational speeds.
The constructions which are selected in the above-mentioned documents with regard to the arrangement of the spring means within the desmodromic valve drives also cannot be transferred readily to valve drives of the type, in which the closing movement of the lifting disk valve is not generated actively by an actuator, but rather by the force of a valve spring which is supported at one end in a stationary manner in the internal combustion engine and at the other end on a spring collar which is moved with the lifting disk valve, and which valve spring has, as is known, a force profile which is dependent on the stroke profile of the lifting disk valve. An additional spring means which is substantially independent of the stroke profile of the lifting disk valve can thus be expedient or required, if it is a lifting disk valve which can be deactivated and if its deactivation is based on a spring collar which can be decoupled from the valve stem and can slide to and fro on the valve stem. A valve drive of this type is apparent from DE 195 22 720 A1, an additional valve spring/disk spring arrangement which is connected rigidly to the valve stem being proposed there for supporting the deactivated lifting disk valve with respect to the valve seat in the case of a decoupled, i.e. pressed down spring collar. However, this additional valve spring/disk spring arrangement is to be considered disadvantageous in so far as it also follows the stroke profile of the lifting disk valve completely and thus leads to an undesirable additional installation space requirement, in particular in the longitudinal direction of the lifting disk valve.